My U.S. Pat. No. 4,332,093 describes a machine which is capable of being moved to the site of a planting, is adapted to undercut a root ball to separate the root ball from the surrounding soil, and to lift the plant with its root ball from the ground for transportation to another site at which the root ball can be wrapped or replanted.
The essential elements of this machine are a tractor or other vehicle, provided with a three-point hitch or like hydraulically controlled structure which can be raised and lowered, a support mounted on this hitch and which can be raised and lowered thereon, and a single spade blade carried by a tool holder on this support which is in the form of a crown and can be given a rotatable movement about its vertical axis so that the spade can reach below the roots of the plant and, upon rotation of the crown, can cut loose a root ball and the plant from the soil.
The spade blade is a single blade rigid with the rotatable crown which has an opening, i.e. is C-shaped, and can be rotated in a C-shaped support crown which is fixed to the chassis and has an opening whose angular extent is substantially equal to that of the rotatable crown. When the inner rotatable crown has its opening aligned with the support crown, i.e. the outer crown, the machine has a C-shaped configuration enabling it to be passed around the plant so that the plant can be centered within the crown to permit the blade to be driven into the ground, e.g. by the tractor movement and then enabling the movable crown to be rotated to free the root ball.
One of the disadvantages of this machine is that it requires the tractor to be brought to a standstill during the operation of the spade blade, i.e. during the portion of the operation of the apparatus in which the root ball is severed from the ground. This means that the tractor must be started and stopped many times in the course of use of the machine, thereby causing deterioration of the vehicle or requiring excessive repair or maintenance procedures.